GxAV Addon does not do anything more than adding static bars
The GxAV addon was last updated on GitHub three years ago.
I didn't test it but I think the addon is broken in the current blender version.
In this case you could try to use an old version of blender.
Older Versions are available here: https://www.blender.org/features/releases/
In your case i would try 2.70 to 2.72

If you don't want to downgrade or can't. I have two more options.


Standard blender functionality "bake sound to f-curves"


Manual entry: 
https://docs.blender.org/manual/de/dev/editors/graph_editor/fcurves/editing.html#bake-sound-to-f-curves


Insert keyframe for the property you want the sound to manipulate.
Select the F-Curve the sound should manipulate

Key->"Bake Sound to F-Curves", select file and frequency, etc.
The bake starts at the current frame position.


Now you have baked you selected fequency range to the F-Curve and you have animation to the sound.

If the amplitude is to small you can use the modifier "Envelope". Add the modifier "Envelope" to the F-Curve. Add a new point in the modifier and ajust the minimum and maximum bounds.

If you want the same "Envelope" modifier for other F-Curves, you can copy and paste them with the buttons right of the "Add modifiers"-Dropdown.


Animation Nodes 



More powerfull but also more learning involved. You need to install the addon and learn how it works.

Download Link: https://github.com/JacquesLucke/animation_nodes/releases

Manual: http://animation-nodes-manual.readthedocs.io/en/latest/


Installation: http://animation-nodes-manual.readthedocs.io/en/latest/user_guide/install/install.html
Sound nodes: http://animation-nodes-manual.readthedocs.io/en/latest/user_guide/nodes/sound/index.html


Simple example:


Install the addon.
Open a node editor window.
Add new NodeTree.
Add the "Bake Sound"-Node.
Click "Load New Sound" and select your sound file.

Click "Bake Average". Now you have baked your average value of the sound file and you can use it.
Rebuild the node setup like in the following picture:



Maybe you have to adjust the channel (see the Video Sequence Editor)
In the "Object Output"-Node, you have to select your target object.
Adjust the mulipication value in the math node.

Now the object should resize to the sound.